So for anybody wondering, here’s my theory to explain everything occurring in the last couple scenes of BBC’s Sherlock…
How and did Sherlock survive falling from the roof? My theory is this…
After Moriarty killed himself, Sherlock’s only course of action in order to save his friends was to kill himself by throwing himself off the building. I think Sherlock came up with the plan to use the body of Moriarty instead! He could put his coat on Moriarty’s body and throw it off the building instead (stick with me here…). As Audra pointed out, during the preceding conversation the references of how Sherlock ‘is’ Moriarty may then also be reversed and Moriarty ‘is’ now Sherlock.
So what about the fact John was watching the whole event? Well, we know John doesn’t have the greatest eyesight in the first place. But when John was first arriving on the scene Sherlock was very explicit about where he wanted John to stand. Notice, Sherlock explicitly positioned John so the sun would be coming up from behind Sherlock, over his shoulder, further blinding John.
What about the fact John saw Sherlock’s body laying on the ground after he fell. Also remember that John ‘saw’ the Hound in the lab in the previous episode. We’re seeing the story through John’s eyes so if he was convinced it was Sherlock, that’s what we would see. Add to that the fact immediately prior he was struck by a biker, fell to the ground knocking his head quite hard, enough there is an audible ‘dazed’ tone we hear as well, further confirming he wasn’t seeing things quite right. John is also a doctor and would know, based on the apparent fall and landing of the body he would almost certainly be dead, which would further enforce his disorientation. Also, Moriarty shot himself in the head (and, I think, landed on his head). And there was a large crowd of people around the body and John never did get all that close. Coupled with everything else, Sherlock could have probably used the body of a dead cat and John would have been convinced it was Sherlock!
What about the fact there would have been an autopsy and the body buried. Remember who would be doing the autopsy… Molly, who Sherlock had a conversation with just prior “I need you”. Between the time of Moriarty killing himself and John arriving an unknown amount of time could have passed. In that time it’s quite possible Sherlock could have called Molly, had her join him on the roof (they were at the hospital after all), and assist him with the disguising of the body and then allowing Moriarty’s body to pass through the system as Sherlock.
As a further, far more speculative and far more unlikely theory, I was thinking possibly the now dead Moriarty was in fact not Moriarty. It was established that Moriarty’s deception was so successful because it was all ‘wrapped up in a truth’, that Moriarty was previously an actor. He gives the story that Sherlock hired him to ‘play Moriarty’. What if yet-unseen real Moriarty is who hired this actor to play Moriarty. Gave him instructions on what to do using the same simple blackmail as he did with Sherlock ‘Kill yourself or everyone you love will die’. If such a scenario is in some way true, it could lend to a very exciting season three… two mastermind ‘ghosts’ pursing each other.